Does it use up a scroll to attempt to write it into your spell book? I think I remember seeing something about this but can't find it. So if you succeed, is the scroll gone? If you fail, is it still gone? Thanks.
If the check succeeds, the wizard understands the spell and can copy it into his spellbook (see Writing a New Spell into a Spellbook). The process leaves a spellbook that was copied from unharmed, but a spell successfully copied from a magic scroll disappears from the parchment.
If the check fails, the wizard cannot understand or copy the spell. He cannot attempt to learn or copy that spell again until one week has passed. If the spell was from a scroll, a failed Spellcraft check does not cause the spell to vanish.
Success gets rid of the scroll, failure gives you another shot at it later.